Steam generating unit



Sept. 20, 1966 L. E. GRIFFITH 3,273,542

STEAM GENERATING UNIT Filed May 19, 1964 r IIIIIIJIIIIfl/IMIIIIIIIIIIIIIIII/II/IIIIIIIIII'IM100M LOUIS E. GRIFFITH INVENTOR United States Patent 3,273,542 STEAM GENERATING UNIT Louis E. Griffith, Worcester, Mass, assignor to Riley Stoker Corporation, Worcester, Mass, a corporation 1 of Massachusetts Filed May 19, 1964, Ser. No. 368,657 2 Claims. (Cl. 12233) This invention relates to a steam generating apparatus and, more particularly, to apparatus arranged to produce steam by the burning of fossil fuels in suspension.

In the burning of fossil fuels for the generation of steam for use in steam turbines, a difiiculty exists in the fact that the heat exchange unit necessary to absorb effective amounts of heat from the products of combustion are quite intricate, thus requiring a large amount of tubing which is bent into intricate forms. At the same time, efficient turbine operation demands that steam be provided at high pressure. When one attempts to form a conventional steam generating unit using tubing of sufficient wall thickness to withstand the high pressures necessary at the turbine, the cost becomes prohibitive. On the other hand, when one attempts to form a steam generating unit with simple forms of high pressure tubing and piping the unit becomes ineffective in removing a satisfactory amount of heat from the products of combustion and a considerable amount of loss occurs because the gas is exhausted at high temperature to the atmosphere. These and other difficulties experienced with the prior art devices have been obviated in a novel manner by the present invention.

It is, therefore, an outstanding object of the invention to provide a steam generating unit which is capable of generating steam at high pressure and yet may be constructed at relatively low cost.

I Another object of this invention is the provision of a steam generating unit receiving heat from the combustion of fossil fuels in which steam at high pressure may be produced wit-h a minimum of high pressure tubing and fittings.

A further object of the present invention is the provision of a steam generating unit in which heat from the combustion of fossil fuels is transmitted to an inert gas at low pressure and this inert gas is used to generate high pressure steam.

It is another object of the instant invention to provide a steam generating unit for the production of high pressure steam wherein a fossil-fired heat exchanger may have its tubes manufactured from low pressure materials and without the high cost, non-corrosive alloys.

With these and other objects in view, as will be apparent to those skilled in the art, the invention resides in the combination of parts set forth in the specification and covered by the claims appended hereto.

The character of the invention, however, may be best understood by reference to one of its structural forms, as illustrated by the accompanying drawings in which:

The single figure shows a steam generating unit embodying the principles of the present invent-ion.

Referring to the drawing, it can be seen that the steam generating unit, indicated generally by the reference numeral 10, consists ofa combustion chamber 11 and a water boiler 12. The combustion chamber is defined by a front wall 13, a rear wall 14, side walls 15, a bottom wall 16, and a roof wall 17, all defining a main chamber 18. At the top portion of the rear wall 14 is an off-take opening 19 leading to a back pass 21 which is connected by a duct 22 to a stack (not shown). A burner 23 is' mounted in the lower part of the front wall 13 and is adapted to mix a fossil fuel with a slight excess of a stoichiometric amount of air to provide for combustion in the main chamber 18. Extending along the intersection of the front wall 13 and 3,273,542 Patented Sept. 20, 1966 the bottom wall 16 is a header 24 which is connected by a duct 25 to a circulating means or circulator, such as a fan 26, adapted to deliver to the header 24 an inert gas, such as helium. Tubes 27 extend from the header 24 up the front wall 13 and along the roof wall 17 toward the back pass 21. Similarly, tubes 28 leave the header 24 and extend along the bottom wall 16 and up the rear wall 14 to the back pass. It will be understood that tubes leaving the header 24 will also extend up the side walls 15 to form part of the heat exchange unit 29 and to terminate in the heater 31. The tubes 27 and 28 at the rear pass are formed into sinuous convolutions to form a convection heat exchange unit 29 and the tubes all terminate in a header 31 located in the back pass. In the back pass 21 at a location downstream of the heat exchange unit 29 is an economizer 32, which will be described more fully hereinafter.

The water boiler 12 is provided with a vertically-elongated housing 33, in the bottom portion of which lies a steaming section 34 and in the upper portion of which lies a steam separator 35. The steaming section consists primarily of straight, vertical tubes 36 which extend from an upper horizontal tube sheet 37 to a lower tube sheet 38. A wall 39 extends between the two sheets and forms a chamber around all of the tubes 36. Bafiies 41 extend transversely of the tubes from the wall 39 in the usual way. The tube sheets 37 and 38 and the wall 39 form a gas chamber 42 around the tubes 36 and the upper part of this gas chamber is connected to the header 31 by a duct 43. Similarly, the lower part of the gas chamber 42 is connected by a duct 44 to the inlet fan 26. The upper ends of the tubes 36 of the steaming unit are connected by a conical ducting 46 to centrifugal separators 47 in the manner shown and suggested in the patent of Kuhner, No. 3,057,333, issued Oct. 9, 1962. The upper part of the separators open into the upper end of the housing 33 which contains another steam separator 48 of the type shown and described in the patent application of Kuhner, Serial Number 310,647, filed Sept. 23, 196 3. Extending from the separator 48 is a pipe 49 leading to a superheater 56 lying in the back pass 21 and connected to the turbine (not shown). Also leading from the separator 48 is a drain pipe 51 leading to the lower part of the housing 33. The lower part of the housing 33 is connected by a pipe 52 to the output end of the economizer 32 located in the back pass 21 of the combustion chamber. The inlet end of the economizer 32 is connected by a pipe 53 to a high pressure pump 54 whose input is connected by a pipe 55 to a hot well (not shown). Since those portions of the unit which contain the inert gas are operated at relatively low pressure, they may be constructed from low cost, low pressure tubing and fittings; for instance, the header 24 and all of the tubes 27 and 28 extending from it, as well as the heat exchange unit 29 and the header 3]., are of low pressure construction.

Similarly, the duct 43 leading to the water boiler 12 and the duct 44 leading away from it, as well as the fan 26 and the duct 25 are of low pressure construction. On the other hand, all of the water circuits associated with the water boiler 12 will be of high pressure construction commensurate with the high pressure steam leading through the pipe 49 to the turbine. This means that the pipe 55, the high pressure pump 54, the pipe 53, and the economizer 32 should be of high pressure construction. Similarly, the pipe 52 leading from the economizer to the water boiler, the housing 33, as well as the pipe 49 leading away from the housing must be of high pressure construction. As is normal in such units, the elements in the interior of a high pressure chamber or housing need not be of high pressure construction, since they are subjected to high pressure on both sides. This would ap ply to the steam separating elements 47 and 48. How- I61, in the case of the steaming unit 34, since the interior f the gas chamber 42 receives gas at low pressure, while 1e exterior of the wall 39, the tube sheets 37 and 38, 1d the interior of the pipes 36 receive the direct high ressure water and steam pressure, this steaming portion IOIlld be of high pressure construction.

The operation of the apparatus will now be readily nderstood in view of the above description. Fuel and ir are introduced into the main chamber 18 of the comustion chamber 11 through the burner 23. Combustion tkCS place and hot products of combustion are generated. he heat is radiated to the walls of the combustion chamer through which flows the inert gas and heat is absorbed y the inert gas. Furthermore, the gas passes over the eat exchange unit 29 so that the inert gas in the interior f the tubing receives even more heat. Eventually, this as is discharged into the header 31 and travels through 1e duct 43 to the water boiler 12. The gas passes downzardly through the gas chamber 42 being directed in a lnuous flow over the exterior of the tubes 36 by means f the baflies 41. Eventually, the gas reaches the bottom f the gas chamber 42 and flows out of the water boiler nd through the duct 44 to the fan 26 where it is forced hrough the duct into the header 24 for recirculation. Vater enters the water boiler through the medium of he high pressure pump 54 which forces the water through he economizer 32 so that the water is preheated before t arrives at the water boiler proper; also, as much heat removed by the economizer from the gases passing lown the back pass into the duct 24 as is necessary to .ssure that the steam generating unit as a whole operates vith a high degree of efiiciency. The preheated water is umped through the pipe 52 to the bottom part of the rousing 33 of the water boiler and enters the body of vater lying therein. The water passes upwardly through he tubes 36 where it is brought into heat exchange relaionship with the inert gas flowing downwardly through he gas chamber 42. The water and gas, therefore, pass n counter-flow with one another to produce optimum teat exchange. Steam is generated in the tubes 36 and asses through the duct 46 to the centrifugal separators L7 where a considerable amount of the steam flows upvardly, while the water removed therefrom drops down nto the main body of water in the boiler. The steam thus eparated passes into the separator 48 and more water 5 removed, the water thus removed flowing through the iipe 59 downwardly into the main body of water in the )oiler. The purified steam, however, passes through the ,ipe 49 to the turbine where it is used to generate elecricity.

It can be seen, then, that all of the pipes and fittings tssociated with the main combustion chamber 11 are of L low cost, low pressure variety. Furthermore, because nert gas is used on the interior of the tubes, there is no ecessity that the tubes be formed of an expensive alloy vhich would resist corrosion, since corrosion is not a problem. On the other hand, the water boiler 12, as is evident in the drawing, is a compact system. A minimum amount of metal and the pressure parts are contained in a small restricted space. Furthermore, the main pressure part, which is the housing 33, is simple in construction and relatively inexpensive to manufacture, so that most of the pressure is carried by a simple pressure vessel. There is a minimum of fittings and connections in the high pressure circuitry, so that the cost is reduced to a very low value.

It is obvious that minor changes may be made in the form and construction of the invention without departing from the material spirit thereof. It is not, however, desired to confine the invention to the exact form herein shown and described, but it is desired to include all such as properly come within the scope claimed.

The invention having been thus described, what is claimed as new and desired to secure by Letters Patent is:

1. A steam generating unit, comprising (a) a combustion chamber having burners mounted on its walls and having tubes designed for relatively low-pressure operation lining its walls and forming a heat exchanger therewith, the chamber having a convection pass means extending therefrom,

(b) a water boiler designed for relatively high-pressure operation having a steaming section and a steamseparating section, the boiler consisting of a vertically-elongated housing having the steaming section with an indirect heat exchange means in its lower portion and the steam separator in the upper portion,

(c) circulation means introducing an inert gas into the tubes of the combustion chamber,

((1) means connecting the tubes of the combustion chamber to the heat exchange means in the steaming section of the water boiler,

(e) means connecting the indirect heat exchange means in the said steaming section to the circulation means, and (f) an economizer located in the said convection pass means and connected directly to the steaming section of the boiler to preheat the water before it reaches the boiler.

2. A steam generating unit as recited in claim 1, wherein the gas is helium.

References Cited by the Examiner UNITED STATES PATENTS FOREIGN PATENTS 3/1959 France. 9/ 1961 Great Britain.

KENNETH W. SPRAGUE, Primary Examiner. 

1. A STEAM GENERATING UNIT, COMPRISING (A) A COMBUSTION CHAMBER HAVING A BURNERS MOUNTED ON ITS WALL AND HAVING TUBES DESIGNED FOR RELATIVELY LOW-PRESSURE OPERATION LINING ITS WALLS AND FORMING A HEAT EXCHANGER THEREWITH, THE CHAMBER HAVING A CONVECTION PASS MEANS EXTENDING THEREFROM, (B) A WATER BOILER DESIGNED FOR RELATIVELY HIGH-PRESSURE OPERATION HAVING A STEAMING SECTION AND A STEAMSEPARATING SECTION, THE BOILER CONSISTING OF A VERTICALLY-ELONGATED HOUSING HAVING THE STEAMING SECTION WITH AN INDIRECT HEAT EXCHANGER MEANS IN ITS LOWER PORTION AND THE STEAM SEPARATOR IN THE UPPER PORTION, (C) CIRCULATION MEANS INTRODUCING AN INERT GAS INTO THE TUBES OF THE COMBUSTION CHAMBER, 